Higher then expected noise on ADAU1961 A/D

We have designed our board with ADAU1961 and SC572 based on SHARC Audio Module.

Our board works great with the exception that we are getting higher than expected noise in DSP from A/D.

We are using fully differential PGA inputs with 0dB gain and no boost, codec is running at 48kHz sample rare as master with I2S serial data format. 

The noise level we measure in DSP is between -65 dBFS to -71dBFS. Based on ADAU1961 data sheet we have expected to see SNR better than 90dB.

We have eliminated possibility that noise is coming from the circuit connected to inputs.

For higher PGA gains the noise is even worse and not acceptable.

To eliminate design or code issues on our side we have also used Bare Metal Framework to generate the code and we have only added noise measurement to it.

We run the test directly on SHARC Audio Module with ADAU1761 (the same as ADAU1961 but with DSP)  and we got noise at -70 dbFS to -76 dBFS.

It's better than our design but still worse than expected.

We also have another board with AKM AK5558 and the same noise measurement is showing -105 dBFS to -109dBFS 

Is this an expected ADAU1961 (ADAU1761) A/D noise performance?

Thank you in advance for any suggestion,

David.